HIGH GENE EXPRESSION OF HIST1H2AG AND HIST1H4A REDUCES IMATINIB UPTAKE INTO CML CELLS AND PREDICTS POOR RESPONSE TO FRONTLINE IMATINIB THERAPY
(Abstract release date: 05/19/16)
EHA Library. Kok C. 06/11/16; 135191; S435
Dr. Chung Hoow Kok
Contributions
Contributions
Abstract
Abstract: S435
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 12:15 - 12:30
Location: Hall A2
Background
Imatinib (IM), the first generation tyrosine kinase inhibitor (TKI), remains standard frontline treatment for newly diagnosed patients with chronic-phase chronic myeloid leukaemia (CP-CML). None of the second generation TKIs have shown an overall survival advantage over IM. We have previously demonstrated that the OCT-1 activity (OA) assay, (which measures the cellular uptake of IM at diagnosis), is highly predictive of subsequent treatment outcomes. To derive an assay more readily adaptable for other labs, and to understand the biological basis of this functional assay we performed gene-expression profiling (GEP) of low and high OA patients.
Aims
To identify a set of genes measured at diagnosis that predicts patients who have high IM uptake (high OA) and favourable clinical outcome.
Methods
RNA was isolated from total white cells collected from patients on TOPS, TIDEL-I and TIDEL-II trials. The OA associated genes were identified based on a pilot microarray study (n=14). Subsequently the identified genes were validated by qRT-PCR in 110 diagnostic CP-CML samples also obtained from these trials. Patients were divided into low and high gene expression groups using the recursive partitioning and regression trees (rpart) with 10-fold cross validation in the training cohort (n=55), and validation in an independent cohort (n=55).
Results
Previous studies have associated low expression of histone genes with higher rates of complete cytogenetic response (CCyR) by 12 months in IM treated patients. We have measured the expression levels by qRT-PCR of 7 histone genes that demonstrated significant association with OA based on our GEP. Importantly, we identified that low expression of 2 histone genes (HIST1H2AG and HIST1H4A based on ΔCt 11.7 and 13.0 cutoff respectively) was significantly associated with high OA in the training cohort, and this was also validated in the independent patient test cohort by both Student’s t-test and rpart statistical methods (Figure 1A). Significantly, in the validation cohort, patients with low expression of these 2 histone genes (histonelow) demonstrated superior rates of major molecular response (MMR: 79% vs 43%, p=0.007) by 12 months, and superior rates of MR4.5 (52% vs 18%, p=0.005) by 24 months compared to patients with high expression of these genes (histonehigh; Figure 1B-C). There were 26 patients in the validation cohort with histonelow based on the cut-offs above, and of these 18 were high OA patients and 8 low OA patients. Although 8/26 (31%) patients were low OA, 7 of these 8 patients achieved MMR by 12 months. There were 6 patients with blast crisis (BC) progression and/or mutations that classified as low OA, and all 6 were in the histonehigh group. The histonehigh group is significantly associated with high blast counts in our study compared to histonelow group (p=0.01), consistent with a previous study that demonstrated BC patients have higher histone GEP compared to CP patients. Furthermore, overexpression of HIST1H2AG using lentiviral transduction significantly reduced the IM cellular uptake in K562 cells compared to empty vector control (p=0.001, Figure 1D), supporting our clinical data observation.
Conclusion
Histone gene expression likely plays a role in regulating the uptake of imatinib, and possibly BC progression. Patients with low expression of HIST1H2AG and HIST1H4A are highly likely to achieve good molecular responses and excellent clinical outcomes on imatinib.
Session topic: Chronic myeloid leukemia - Clinical
Keyword(s): BCR-ABL, Chronic myeloid leukemia, Gene expression, Molecular response
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 12:15 - 12:30
Location: Hall A2
Background
Imatinib (IM), the first generation tyrosine kinase inhibitor (TKI), remains standard frontline treatment for newly diagnosed patients with chronic-phase chronic myeloid leukaemia (CP-CML). None of the second generation TKIs have shown an overall survival advantage over IM. We have previously demonstrated that the OCT-1 activity (OA) assay, (which measures the cellular uptake of IM at diagnosis), is highly predictive of subsequent treatment outcomes. To derive an assay more readily adaptable for other labs, and to understand the biological basis of this functional assay we performed gene-expression profiling (GEP) of low and high OA patients.
Aims
To identify a set of genes measured at diagnosis that predicts patients who have high IM uptake (high OA) and favourable clinical outcome.
Methods
RNA was isolated from total white cells collected from patients on TOPS, TIDEL-I and TIDEL-II trials. The OA associated genes were identified based on a pilot microarray study (n=14). Subsequently the identified genes were validated by qRT-PCR in 110 diagnostic CP-CML samples also obtained from these trials. Patients were divided into low and high gene expression groups using the recursive partitioning and regression trees (rpart) with 10-fold cross validation in the training cohort (n=55), and validation in an independent cohort (n=55).
Results
Previous studies have associated low expression of histone genes with higher rates of complete cytogenetic response (CCyR) by 12 months in IM treated patients. We have measured the expression levels by qRT-PCR of 7 histone genes that demonstrated significant association with OA based on our GEP. Importantly, we identified that low expression of 2 histone genes (HIST1H2AG and HIST1H4A based on ΔCt 11.7 and 13.0 cutoff respectively) was significantly associated with high OA in the training cohort, and this was also validated in the independent patient test cohort by both Student’s t-test and rpart statistical methods (Figure 1A). Significantly, in the validation cohort, patients with low expression of these 2 histone genes (histonelow) demonstrated superior rates of major molecular response (MMR: 79% vs 43%, p=0.007) by 12 months, and superior rates of MR4.5 (52% vs 18%, p=0.005) by 24 months compared to patients with high expression of these genes (histonehigh; Figure 1B-C). There were 26 patients in the validation cohort with histonelow based on the cut-offs above, and of these 18 were high OA patients and 8 low OA patients. Although 8/26 (31%) patients were low OA, 7 of these 8 patients achieved MMR by 12 months. There were 6 patients with blast crisis (BC) progression and/or mutations that classified as low OA, and all 6 were in the histonehigh group. The histonehigh group is significantly associated with high blast counts in our study compared to histonelow group (p=0.01), consistent with a previous study that demonstrated BC patients have higher histone GEP compared to CP patients. Furthermore, overexpression of HIST1H2AG using lentiviral transduction significantly reduced the IM cellular uptake in K562 cells compared to empty vector control (p=0.001, Figure 1D), supporting our clinical data observation.
Conclusion
Histone gene expression likely plays a role in regulating the uptake of imatinib, and possibly BC progression. Patients with low expression of HIST1H2AG and HIST1H4A are highly likely to achieve good molecular responses and excellent clinical outcomes on imatinib.
Session topic: Chronic myeloid leukemia - Clinical
Keyword(s): BCR-ABL, Chronic myeloid leukemia, Gene expression, Molecular response
Abstract: S435
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 12:15 - 12:30
Location: Hall A2
Background
Imatinib (IM), the first generation tyrosine kinase inhibitor (TKI), remains standard frontline treatment for newly diagnosed patients with chronic-phase chronic myeloid leukaemia (CP-CML). None of the second generation TKIs have shown an overall survival advantage over IM. We have previously demonstrated that the OCT-1 activity (OA) assay, (which measures the cellular uptake of IM at diagnosis), is highly predictive of subsequent treatment outcomes. To derive an assay more readily adaptable for other labs, and to understand the biological basis of this functional assay we performed gene-expression profiling (GEP) of low and high OA patients.
Aims
To identify a set of genes measured at diagnosis that predicts patients who have high IM uptake (high OA) and favourable clinical outcome.
Methods
RNA was isolated from total white cells collected from patients on TOPS, TIDEL-I and TIDEL-II trials. The OA associated genes were identified based on a pilot microarray study (n=14). Subsequently the identified genes were validated by qRT-PCR in 110 diagnostic CP-CML samples also obtained from these trials. Patients were divided into low and high gene expression groups using the recursive partitioning and regression trees (rpart) with 10-fold cross validation in the training cohort (n=55), and validation in an independent cohort (n=55).
Results
Previous studies have associated low expression of histone genes with higher rates of complete cytogenetic response (CCyR) by 12 months in IM treated patients. We have measured the expression levels by qRT-PCR of 7 histone genes that demonstrated significant association with OA based on our GEP. Importantly, we identified that low expression of 2 histone genes (HIST1H2AG and HIST1H4A based on ΔCt 11.7 and 13.0 cutoff respectively) was significantly associated with high OA in the training cohort, and this was also validated in the independent patient test cohort by both Student’s t-test and rpart statistical methods (Figure 1A). Significantly, in the validation cohort, patients with low expression of these 2 histone genes (histonelow) demonstrated superior rates of major molecular response (MMR: 79% vs 43%, p=0.007) by 12 months, and superior rates of MR4.5 (52% vs 18%, p=0.005) by 24 months compared to patients with high expression of these genes (histonehigh; Figure 1B-C). There were 26 patients in the validation cohort with histonelow based on the cut-offs above, and of these 18 were high OA patients and 8 low OA patients. Although 8/26 (31%) patients were low OA, 7 of these 8 patients achieved MMR by 12 months. There were 6 patients with blast crisis (BC) progression and/or mutations that classified as low OA, and all 6 were in the histonehigh group. The histonehigh group is significantly associated with high blast counts in our study compared to histonelow group (p=0.01), consistent with a previous study that demonstrated BC patients have higher histone GEP compared to CP patients. Furthermore, overexpression of HIST1H2AG using lentiviral transduction significantly reduced the IM cellular uptake in K562 cells compared to empty vector control (p=0.001, Figure 1D), supporting our clinical data observation.
Conclusion
Histone gene expression likely plays a role in regulating the uptake of imatinib, and possibly BC progression. Patients with low expression of HIST1H2AG and HIST1H4A are highly likely to achieve good molecular responses and excellent clinical outcomes on imatinib.
Session topic: Chronic myeloid leukemia - Clinical
Keyword(s): BCR-ABL, Chronic myeloid leukemia, Gene expression, Molecular response
Type: Oral Presentation
Presentation during EHA21: On Saturday, June 11, 2016 from 12:15 - 12:30
Location: Hall A2
Background
Imatinib (IM), the first generation tyrosine kinase inhibitor (TKI), remains standard frontline treatment for newly diagnosed patients with chronic-phase chronic myeloid leukaemia (CP-CML). None of the second generation TKIs have shown an overall survival advantage over IM. We have previously demonstrated that the OCT-1 activity (OA) assay, (which measures the cellular uptake of IM at diagnosis), is highly predictive of subsequent treatment outcomes. To derive an assay more readily adaptable for other labs, and to understand the biological basis of this functional assay we performed gene-expression profiling (GEP) of low and high OA patients.
Aims
To identify a set of genes measured at diagnosis that predicts patients who have high IM uptake (high OA) and favourable clinical outcome.
Methods
RNA was isolated from total white cells collected from patients on TOPS, TIDEL-I and TIDEL-II trials. The OA associated genes were identified based on a pilot microarray study (n=14). Subsequently the identified genes were validated by qRT-PCR in 110 diagnostic CP-CML samples also obtained from these trials. Patients were divided into low and high gene expression groups using the recursive partitioning and regression trees (rpart) with 10-fold cross validation in the training cohort (n=55), and validation in an independent cohort (n=55).
Results
Previous studies have associated low expression of histone genes with higher rates of complete cytogenetic response (CCyR) by 12 months in IM treated patients. We have measured the expression levels by qRT-PCR of 7 histone genes that demonstrated significant association with OA based on our GEP. Importantly, we identified that low expression of 2 histone genes (HIST1H2AG and HIST1H4A based on ΔCt 11.7 and 13.0 cutoff respectively) was significantly associated with high OA in the training cohort, and this was also validated in the independent patient test cohort by both Student’s t-test and rpart statistical methods (Figure 1A). Significantly, in the validation cohort, patients with low expression of these 2 histone genes (histonelow) demonstrated superior rates of major molecular response (MMR: 79% vs 43%, p=0.007) by 12 months, and superior rates of MR4.5 (52% vs 18%, p=0.005) by 24 months compared to patients with high expression of these genes (histonehigh; Figure 1B-C). There were 26 patients in the validation cohort with histonelow based on the cut-offs above, and of these 18 were high OA patients and 8 low OA patients. Although 8/26 (31%) patients were low OA, 7 of these 8 patients achieved MMR by 12 months. There were 6 patients with blast crisis (BC) progression and/or mutations that classified as low OA, and all 6 were in the histonehigh group. The histonehigh group is significantly associated with high blast counts in our study compared to histonelow group (p=0.01), consistent with a previous study that demonstrated BC patients have higher histone GEP compared to CP patients. Furthermore, overexpression of HIST1H2AG using lentiviral transduction significantly reduced the IM cellular uptake in K562 cells compared to empty vector control (p=0.001, Figure 1D), supporting our clinical data observation.
Conclusion
Histone gene expression likely plays a role in regulating the uptake of imatinib, and possibly BC progression. Patients with low expression of HIST1H2AG and HIST1H4A are highly likely to achieve good molecular responses and excellent clinical outcomes on imatinib.
Session topic: Chronic myeloid leukemia - Clinical
Keyword(s): BCR-ABL, Chronic myeloid leukemia, Gene expression, Molecular response
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